1. Field of the Invention
The present invention relates to a field effect transistor (FET) power amplifying apparatus, particularly to an FET linear power amplifying apparatus for single side band (SSB) multiplex communication systems.
2. Description of the Prior Art
In conventional linear power amplifying apparatuses for SSB multiplex communication systems traveling-wave tubes (TWT) are used for linear power amplification and such an apparatus contains various problems. For example, the characteristics of the TWT change as the TWT ages, the TWT manufacturing costs are high and the TWT has a high power consumption.
Recently, the power amplifying performance of FETs has been up-graded, and FETs are now widely used for linear power amplification. However, FET linear power amplifying apparatuses contain problems in that distortion characteristics and gain characteristics change in proportion to changes in ambient temperature.